Conventionally, the light source device including the light source and the lightguide element that guides the light emitted from the light source is proposed in order to improve use efficiency of the light emitted from the light source (for example, see JP-A-2013-218826).
For example, the light source device disclosed in JP-A-2013-218826 includes a light source, a first concave mirror that reflects the light emitted in a first direction, and a second concave mirror that reflects the light emitted in a second direction. The first concave mirror is formed into a curved shape having a focal point in section, a position where the light source emits the light in the first direction is substantially matched with the focal point, the light emitted in the first direction is reflected by the first concave mirror to exit to the outside, and the light emitted in the second direction is reflected by the second concave mirror, and is reflected by the first concave mirror to exit to the outside. The first and second concave mirrors are formed as a cylindrical surface.
However, in the light source device disclosed in JP-A-2013-218826, because the two concave mirrors are formed as the cylindrical surface, each concave mirror has power only in one direction, but does not have power in a direction orthogonal to the direction in which the concave mirror has the power. In a total of light emitted from the light source, for light perpendicularly incident on the concave mirror in the direction in which the concave mirror does not have the power, because the position of the light does not change in the direction even if the light is reflected by the concave mirror, only the light is reflected between the two concave mirrors, but the light does not exit from the light source device. Therefore, the light becomes a loss. Therefore, there is a demand for the light source device having the higher light use efficiency.